Electric circuit interrupter



1958 T. J. scuLLY ELECTRIC CIRCUIT INTERRUPTER Filed Dec. 15. 1954 INVENTOR Trips J. SCULLY,

BY AT ORNEY.

r' 2,861,152 1C6 Patented Nov. 18, 1958 ELECTRIC CIRCUIT INTERRUPTER Thomas J. Scul ly, Bridgeport, Pa., assignor to General a Electric Company, a corporation of New York a Application December 13, 1954, Serial No. 474,782 2 Claims. (or. 200-144 p This invention relates to an electric circuit interrupter and, more particularly, to an arc-extinguishing devicefor such an interrupter.

For effectively extinguishing the are which is established during circuit interruption, it has been proposed .heretofore to maintain the are from its very inception within a narrow, closely-confining slot'bounded by insulating material. Examples of interrupters which utilize this principle of operation are disclosed and claimed in Seaman Patent 2,429,846, and Titus Patent 2,632,826, both of which are assigned to the assignee of the present .invention. Another method for extinguishing the arc is .to drive it against the exposed edges of a series of spacedapart metallic plates. The edges act to split the are into a plurality of serially related arclets which are subsequently deionized and extinguished as they move within the spaces between the plates. Each of these methods of arc-extinction has its own particular advantages, and it is a primary object of my invention to provide a circuit interrupter which effectively Intilize s both of these arc-extinguishing methods.

The interrupting ability of a metallic-plate type of arcextinguisher depends upon the number of plates included within the extinguisher and upon the spacing between the individual plates. The spacing between the individual plates should generally conform to a predetermined optimum value if efficient utilization of the plates is to be expected. With this spacing so selected and with the overall size of the arc-extinguisher limited to a predetermined maximum value, it is a further object of my invention to construct the arc-extinguisher in such a manner that an exceptionally large number of arcsplitting plates may be included therein.

7 To provide more than a certain limited number of plates for an arc chute of a predetermined size gives :rise to the difficulty that certain of the plates will be so remote from the arc-initiation region that they will be unable to effectively contribute to the arc-extinction process. Accordingly, it is another object of my invention to insure that all of the plates, including even the remote plates, effectively contribute to the arc-extinction process.

;In' accordance with one form of my invention, -1 provide' an arc chute comprising transversely-spaced barvriersfforming a narrow slot therebetween. A first group of transversely-extending, spaced-apart metallic plates is stacked across the slot along one side of the chute and a second group of spaced-apart plates is stacked across the slot along a side of said chute which intersects said ;one side. The arc is initiated within the slot at a point tion of the arc-produced gases will flow through the port. Such flow is effective to sweep the are into engagement with the more remote plates, thereby insuring that these plates effectively contribute to the arc extinguishing process. i I

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. In the drawing, Fig. l is a cross sectional view of one form of circuit interrupter constructed in accordance with my invention. Fig. 1 has been taken along the line I-I of Fig. 2. Fig. 2 is a cross-sectional View taken along the line IIII of Fig. l, and Fig. 3 is an exploded view illustrating certain components of the interrupter shown in Figs. 1 and 2.

Referring more particularly to the drawing, I have shown a single pole circuit interrupter comprising relatively movable contacts 10 and 12 which are separable to interrupt a circuit which extends through the interrupter. In Fig. 1 the interrupter is shown in open-circuit position with the movable contact 10 having been separated from the stationary contact 12. Relative movement between these contacts is effected by means of a suitable operating mechanism (not shown) coupled to the movable contact 10 by an operating link 13. When the contacts 10, 12 are moved into engagement, a circuit is established which extends from a terminal stud 15, through conductive supports 17 and 18, the stationary contact 12, the movable contact 10, then through a suitable flexible conductor 20 to the opposite terminal stud (not shown).

Preferably, the interrupter is of the multiple-contact type described and claimed in the aforementioned Titus patent, so that each pole of the interrupter comprises a plurality of narrow stationary contacts connected in parallel-circuit relationship and a plurality of cooperating movable contacts mechanically-coupled together and similarly connected in parallel-circuit relationship. The stationary contacts are best seen in Fig. 2 wherein they are designated 12 and 12a. To provide for the desired wipe between the relatively-movable contacts, the stationary contacts 12 and 12a are mounted for limited pivotal movement about a fixed pivot pin 22. A suitable compression spring such as 23 urges the stationary contact toward the movable contact, but a stop 24 serves to limit this movement. This type of contact structure is generally well known, and its details form no partof my invention.

For extinguishing the arc which is drawn between the contacts when they are separated, I provide a novel form of arc-extinguishing device which is generally illustrated at 30. This device 30, hereinafter designated an arc chute, is suitably mounted in stationary relationship about the separable contacts and comprises a pair .of transversely-spaced side walls 31 and 32. The space between these side walls is generally enclosed except for an outlet 49 provided at the top of the chute. Mounted between the side walls are a plurality of insulating barriers which form a pair of narrow slots 33 and 34, best seen in Fig.. 2. In each of these slots a different pair of separable contacts is operatively mounted. As shown in Fig. 2, this plurality of barriers comprises a pair of outer barriers 35 and 36, a pair of intermediate barriers 37 and 38, and a central barrier 40. The outer barriers 35 and 36 are recessed to form vertically-extending pockets 42. The intermediate barriers are provided with vertically-elongated passageways 43 extending therethrough, and the central barrier contains a series of transversely extending perforations 44. Suitable tie-bolts such as 45 clamp all of the-barriers together in relatively fixed relationship. Each of the ".contact receiving slots 33 and 34 is bound ed by the central barrier 40 and one of the intermediate barriers 37 or 38. These slot-defining barriers 37, 38, and 40 are maintained in spaced apart relationship by suitable spacers interposed therebetween. One of such spacers is located between barriers 37 and 38 at the lower end of the arc chute, as may be seen at 48.

When the contacts are separated, a pair of arcs is established, one within each of the slots 33 and 34. The perforations 44 in the center barrier assure that arcs are formed in both of the slots and, thus, prevent the possibility that only a single slot will be required to carry the entire current. For example, should an are be established initially in only one of the slots, the resulting gases are rapidly transferred through the perforations 44 into the other slot and will immediately cause a second arc to be established between the contacts located in the other slot.

The elongated passages 43 which extend through the intermediate barriers 37 and 38 serve two distinct functions. The first of these functions is to minimize the possibility that sneak currents will be conducted along the surfaces of the intermediate barrier at a time when these surfaces have become overheated from the arc. The second of these functions is to provide a means for laterally venting a portion of the arc-produced gases from the slots 33, 34 to the vertically-extending side pockets 42. This renders the gases more turbulent and rapidly exposes additional cooling surfaces to them .of spaced-apart metallic plates. One of these stacks 50 extends along the top side of the arc chute and partially across the outlet 49. The other of these stacks 51 extends along a vertical side of the chute which is remote from the arc-initiation region, i. e., the region in which .the contacts 10, 12 initially part. When an arc is driven against either of these stacks, the exposed edges of the individual plates split the are into a plurality of seriallyrelated arclets which then move into the spaces between the plates. When propelled through these interplate spaces, the arclets rapidly transfer their heat to the cool surfaces of the adjacent metallic plates. This action, combined with the turbulent gas-mixing action which occurs as the arclets are thus propelled, rapidly deionizes and extinguishes the arclets, thereby interrupting the provided between the adjacent plates, as may be seen in Fig. 2. As will also be seen in Figs; 1 and 2, the inner or arc-splitting edges of the metallic plates 53 extend between the side walls 31 and 32 by paths disposed generally perpendicular to the side walls. Vertically aligned with the metallic plates 53 are corresponding insulating plates 55, adjacent ones of which are spaced apart by the insulating strips 54. These insulating plates '55 serve to cool the streams of arcing gases which flow through the interplate spaces and additionally maintain these streams segregated until safely cooled, thereby minimizing the possibility of an are being established exterior to the metallic plates. As shown, the metallic plates 53, the insulating plates 55, and the spacer strips '54 are all clamped together by four insulated rods 57 4 which extend across the top of the arc chute. These rods 57, which are suitably anchored in appropriate blocks 58 and S9 fixed to the side walls 31 and 32, also serve to hold the stack 50 in a stationary position relative to the side walls.

The vertically extending stack 51 is constructed in a manner similar to the stack 50. This stack 51 comprises metallic plates 60 which are maintained in the desired spaced apart relationship by spacer strips 61 corresponding to the previously-described spacer strips 54. These spacer strips 61 extend over only a portion of the transverse width of the metallic plates, thereby leaving relatively wide interplate passageways at the central region of adjacent plates. For reasons which will soon appear more clearly, these metallic plates of stack 51 are arranged to slope upwardly towards the outlet of the chute. This slope is obtained by providing the anchoring blocks 58 with suitably inclined lower surfaces against which the stack 51 is secured by suitable bolts (not shown).

Additional features of my arc chute will appear more clearly from the following description of a circuit interrupting action. Assume first that the pairs of separable contacts are initially closed and that they are then separated to establish a pair of high-current, large-diameter arcs Within the slots 33 and 34. These arcs immediately generate large amounts of gases which are turbulently impelled through the laterally-extending passageways 43 and through the slots 33, 34. The result is a combined cooling and turbulent mixing effect which rapidly increases the resistance of the arcs and lessens their diameter and current content. As this process is taking place .and as the moving contacts continue to separate from the stationary contacts, the terminal portions of the arcs are rapidly transferred to a pair of suitable arc runners 65, 66 which extend through the arc chute and toward the arc-splitting stacks 50, 51. Under the influence of thermal and magnetic loop forces acting in a well-known manner, the arc terminal portions then move rapidly along these runners and out toward the stacks 50, 51. This movement is accelerated by suitable magnetizable plates 67 secured to the outer sidewalls 31 and 32. These plates 67 together with the metallic plates in stacks 50, 51 provide a low reluctance magnetic path which distorts the field surrounding the arc and produces magnetic blowout forces acting to drive the arc toward the stacks. As the arcs move outwardly at high speed along the runners 65 and 66, their resistance is further increased by elongation, as well as by additional cooling and gaseous mixing actions. Finally, these high resistance arcs, which are then relatively vulnerable to extinction are driven against the edges of the metallic platesin the stacks 50 and 51. As previously explained, these edges immediately split each of the arcs into a plurality of serially-related arclets which quickly move into the spaces between the plates. These arclets are then propelled through the interplate spaces where they are further deionized and finally. extinguished, thereby interrupting the circuit.

The interrupting ability of the arc-splitting stacks.de pends upon the number of plates used, the spacing between the plates, and the effectiveness with which the plates are utilized. In order to permit the Used an exceptionally large number of plates, I have constructed the arc chute so that the plates may be stacked along both the horizontal and vertical sides of the chute. As seen in Fig. 1, the vertically-extending stack 51 has been located inwardlyfrom the vertical end wall 70 of the interrupter so that a vertically-extending exhaust duct 71 is formed between the wall 70 and the stack 51. The arcing gases which flow through the vertically-extending stack 51, which is located between the arc-initiation region and. the exhaust duct 71, fiow upwardly through the exhaust duct 71 andv then through the outlet 49. ,Thus, 'even'though the arcrchute has an outlet only at.its upper end, I. am not limited to a single stack extending horizontally across this upper outlet area. The verticallyextending duct 71 permits the use of a vertically-extending stack as well as the horizontally extending stack.

With stacks extending across both the horizontal and vertical sides of the chute, certain of the plates will be so remote from the point of arc-initiation that there is.

a danger that they will be unable to effectively contribute to the arc-extinction process. For example, those plates which are located in the region diagonally-opposed to the arc-initiation point, i. e., at the upper left hand corner of the chute as seen in Fig. 1, are less likely to engage the arc than are those which are located closer to the arc initiation point, e. g., those at the bottom of stack 51 or at the right hand side of stack 50. To preclude this danger, in accordance with my invention, the stacks 50 and 51 have been spaced apart by a relatively large distance in the region which is diagonally-opposed to the arc-initiation point. This provides an exhaust port 73 of a relatively large cross-sectional area in that region of the chute which is the most remote from the arc-initiation point. This large effective area coupled with the fact that arc-generated gases can follow a substantially straight line path in flowing from the arc-initiation point through the exhaust port 73 effectively contribute to the low fluid-resistance of this region. Through this region of low fluid-resistance, the arcing gases move at high speed, sweeping the are into arc-splitting engagement with those plates located adjacent the port 73. There is sufiicient flow through the other interplate spaces to insure that the other plates will share in the arc-extinguishing process.

To insure that sufficient flow will take place through the vertical bafiie stack 51, the plates 60 therein, instead of being horizontally disposed, are upwardly and outwardly inclined toward the outlet area of the chute, as previously described. This permits the arcing gases to flow between the plates 60 and into the exhaust vent 71 without abrupt change of direction. As a result, the resistance of the vertical stack 51 to fluid flow is lowered and is more nearly equal to that of stack 50. Accordingly, the flow is distributed more evenly between these two stacks.

To further accelerate the desired movement of the arc into the arc-splitting stacks, I have provided-a series of turbulence-producing recesses in the opposite surfaces of the central barrier 40 adjacent its lower end. As may be seen in Figs. 1 and 3, these recesses comprise a slot 75 on each side of the central barrier and a group of irregularly-shaped, staggered openings 76 thereadjacent. These recesses are located between the arc-initiation point and the openings in the lower end of the chute through which the movable contacts extend. Because of these recesses, the pathways through these lower openings are tortuous and rough-surfaced. As a result, those aregenerated gases which tend to flow downwardly as the contacts are separated are subjected to a high degree of turbulence in this region which tends to block this down ward flow and to promote the flow of gases upwardly and outwardly through the stacks 50, 51 and through the exhaust port 73. This upward and outward flow sweeps the are into the stacks as desired. The barrier spacer 48, which is located adjacent the bottom of the arc extinguishing device, also restricts the downward exit of the arcproduced gases and promotes an upward and outward flow of these gases. To this end, the spacer 48 is shaped to enclose substantially the entire lower righthand corner of the chute, as seen in Fig. 1.

When the arclets which are formed in the interplate spaces of stacks 50 and 51 are propelled across the surfaces of the plates, there is a tendency for them to change their shape and produce varying magnetic forces which tend to reverse their direction of motion. As a result, it frequently happens that these arclets are repetitively propelled back and forth across these plates before final extinction occurs. I have found that the arclets, when moving in this manner, tend to produce a localized overheatingof any solid insulation which may be disposed adjacent the front edges of the plates. This gives rise to the possibility that an incipient breakdown pathwill be formed along the surface of any such insulation which extends between these front edges. To minimize this possibility, my central and intermediate barriers 40, 37, and 38 are dimensioned in such a manner that a relatively large space is provided between the outer edges of the barriers and the front edges of the plates. As may be seen in Figs. 1 and 3, this is especially true of the center barrier which is provided with an edge defining the boundary of a large space of a generally triangular configuration.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent is:

1. In a circuit interrupter, an arc chute comprising a first group of transversely-extending, spaced-apart metallic plates stacked along one side of said chute, a second group of transversely-extending, spaced-apart plates stacked along a side of said chute which intersects said one side, a pair of relatively-movable switch parts separable to initiate an are at a predetermined location within said chute, means extending through a restricted opening in said chute for effecting relative movement of said switch parts, means for propelling said are into engagement with said groups of plates, said groups of plates being spaced apart to form an exhaust port located in a region of said chute which is generally more remote from said are initiation point than are the majority of said plates, said exhaust port having a substantially larger effective venting area than the venting area between adjacent plates in each of said groups, and means for inhibiting the flow of arc-generated gases through said restricted opening comprising a series of irregularlyshaped, turbulence-producing recesses formed in the portion of said chute adjacent said restricted opening.

2. In a circuit interrupter, an arc chute comprising transversely-spaced barriers defining a narrow slot therebetween, means enclosing a major portion of said slot and providing an outlet at one end of said chute, means comprising a pair of relatively movable switch parts for initiating an are within said slot at a point adjacent an opposite end of said chute, means extending through a restricted opening in said chute for effecting relative movement of said switch parts, means for inhibiting the flow of arc-generated gases through said restricted opening comprising a plurality of irregularly-shaped, staggered recesses formed in at least one of said barriers in the vicinity of said opening, said arc-initiation point being located at one side of said chute, an exhaust duct extending along an opposite side of said chute and into communication with said outlet, a first group of transverselyextending, spaced-apart metallic plates stacked across a portion of said outlet, and a second group of transverselyextending spaced-apart metallic plates stacked along said exhaust duct between said duct and said arc-initiation region.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,463 Hilliard Apr. 18, 1933 1,919,438 Lindstrom July 25, 1933 2,180,147 Hopp Nov. 14, 1939 (Other references on following page) 7 UNITED STATES PATENTS Nau Mar. 17, 1942 Boe-hne -Aug.' 18,- 1942 "Walls Dec; 28, 1943 1 Seaman Oct. 28, 1947 8 Favre Oct. 21, 1952 "Ridgley June '23, 1953 Spears .4 Feb. 14 19-56 FOREIGN PATENTS France May28,- 1929 

